基于远场可变孔径的高斯函数拟合测量模场直径

Measurement of single mode fiber field diameter with gaussian fitting based on variable aperture of far field

模场直径作为单模光纤的一个关键参数,由基模的模场分布而决定。单模光纤基模的横向电场强度分布接近于高斯分布。通过远场可变孔径法能测量出一组多孔径远场辐射光功率数据。本文将此数据转化得到光纤的出射光场分布,并使用高斯函数对出射光场分布进行数值拟合校正,最后由拟合得到的高斯函数分布求得模场直径。实验表明,标准仪器在测量条件良好条件下测得模场直径为9.090μm,在测量条件变差时测得的模场直径为8.794μm,存在3.2%的相对误差,而使用高斯函数拟合方法测得的前后模场直径数据为9.089μm、9.061μm,仅存在0.3%的相对误差。对比多次数据后发现本文方法可以有效消除在实际测量过程中的偶然误差,如由于被测光纤模场中心与透光孔中心偏离引起的测量误差,提高了模场直径测量结果的稳定性和准确性。

The mode field diameter is an important parameter to evaluate the performance of single-mode fiber.The mode field diameter is determined by the mode field distribution of the fundamental mode.The transverse electric field intensity distribution of the single mode fiber is similar to the Gaussian distribution.The variable aperture method in the far field is used to measure the far field radiation power data,and then the optical field distribution of the optical fiber end face is obtained.The Gaussian function is used to calibrate the measured data,and then the diameter of the mold field is obtained from the Gaussian function distribution obtained from the fitting.The experimental results showed that the measured mode field diameter of standard instrument was 9.090μm under good measuring conditions,and the measured mode field diameter of standard instrument was 8.794μm under bad measuring conditions,with a relative error of 3.2%,while the measured mode field diameter of Gaussian function fitting method was 9.089μm and 9.061μm,with a relative error of 0.3%.After many comparisons,it is found that this method can effectively eliminate the accidental errors in the actual measurement process,such as the measurement errors caused by the deviation between the mode field center of the measured fiber and the center of the pervious hole,thus improving the stability and accuracy of the measurement results of the mode field diameter.